Integrated process for in-situ organic peroxide production and oxidative heteroatom conversion

ABSTRACT

An oxidative treatment process, e.g., oxidative desulfurization or denitrification, is provided in which the oxidant is produced in-situ using an aromatic-rich portion of the original liquid hydrocarbon feedstock. The process reduces or replaces the need for the separate introduction of liquid oxidants such as hydrogen peroxide, organic peroxide and organic hydroperoxide in an oxidative treatment process.

RELATED APPLICATIONS

Not applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to integrated oxidation processes toefficiently reduce the sulfur and nitrogen content of hydrocarbons toproduce fuels having reduced sulfur and nitrogen levels.

2. Description of Related Art

The discharge into the atmosphere of sulfur compounds during processingand end-use of the petroleum products derived from sulfur-containingsour crude oil pose health and environmental problems. The stringentreduced-sulfur specifications applicable to transportation and otherfuel products have impacted the refining industry, and it is necessaryfor refiners to make capital investments to greatly reduce the sulfurcontent in gas oils to 10 parts per million by weight (ppmw), or less.In industrialized nations such as the United States, Japan and thecountries of the European Union, refineries for transportation fuel havealready been required to produce environmentally clean transportationfuels. For instance, in 2007 the United States Environmental ProtectionAgency required the sulfur content of highway diesel fuel to be reduced97%, from 500 ppmw (low sulfur diesel) to 15 ppmw (ultra-low sulfurdiesel). The European Union has enacted even more stringent standards,requiring diesel and gasoline fuels sold in 2009 to contain less than 10ppmw of sulfur. Other countries are following in the direction of theUnited States and the European Union and are moving forward withregulations that will require refineries to produce transportation fuelswith an ultra-low sulfur level.

To keep pace with recent trends toward production of ultra-low sulfurfuels, refiners must choose among the processes or crude oils thatprovide flexibility to ensure that future specifications are met withminimum additional capital investment, in many instances by utilizingexisting equipment. Conventional technologies such as hydrocracking andtwo-stage hydrotreating offer solutions to refiners for the productionof clean transportation fuels. These technologies are available and canbe applied as new grassroots production facilities are constructed.However, many existing hydroprocessing facilities, such as those usingrelatively low pressure hydrotreaters were constructed before these morestringent sulfur reduction requirements were enacted and represent asubstantial prior investment. It is very difficult to upgrade existinghydrotreating reactors in these facilities because of the comparativelymore severe operational requirements (i.e., higher temperature andpressure conditions) to obtain clean fuel production. Availableretrofitting options for refiners include elevation of the hydrogenpartial pressure by increasing the recycle gas quality, utilization ofmore active catalyst compositions, installation of improved reactorcomponents to enhance liquid-solid contact, the increase of reactorvolume, and the increase of the feedstock quality.

There are many hydrotreating units installed worldwide producingtransportation fuels containing 500-3000 ppmw sulfur. These units weredesigned for, and are being operated at, relatively mild conditions,i.e., low hydrogen partial pressures of 30 kilograms per squarecentimeter for straight run gas oils boiling in the range of 180°C.-370° C.

However, with the increasing prevalence of more stringent environmentalsulfur specifications in transportation fuels mentioned above, themaximum allowable sulfur levels are being reduced to no greater than 15ppmw, and in some cases no greater than 10 ppmw. This ultra-low level ofsulfur in the end product typically requires either construction of newhigh pressure hydrotreating units, or a substantial retrofitting ofexisting facilities, e.g., by integrating new reactors, incorporatinggas purification systems, reengineering the internal configuration andcomponents of reactors, and/or deployment of more active catalystcompositions. Each of these options represents a substantial capitalinvestment

Sulfur-containing compounds that are typically present in hydrocarbonfuels include aliphatic molecules such as sulfides, disulfides andmercaptans, as well as aromatic molecules such as thiophene,benzothiophene and its long chain alkylated derivatives, anddibenzothiophene and its alkyl derivatives such as4,6-dimethyl-dibenzothiophene. Aromatic sulfur-containing molecules havea higher boiling point than aliphatic sulfur-containing molecules, andare consequently more abundant in higher boiling fractions.

In addition, certain fractions of gas oils possess different properties.The following table illustrates the properties of light and heavy gasoils derived from Arabian Light crude oil:

TABLE 1 Feedstock Name Light Heavy API Gravity ° 37.5 30.5 Carbon wt %85.99 85.89 Hydrogen wt % 13.07 12.62 Sulfur wt % 0.95 1.65 Nitrogenppmw 42 225 ASTM D86 Distillation IBP/5 V % ° C. 189/228 147/244 10/30 V% ° C. 232/258 276/321 50/70 V % ° C. 276/296 349/373 85/90 V % ° C.319/330 392/398   95 V % ° C. 347 Sulfur Speciation OrganosulfurCompounds ppmw 4591 3923 Boiling Below 310° C. Dibenzothiophenes ppmw1041 2256 C₁-Dibenzothiophenes ppmw 1441 2239 C₂-Dibenzothiophenes ppmw1325 2712 C₃-Dibenzothiophenes ppmw 1104 5370

Aliphatic sulfur-containing compounds are more easily desulfurized(labile) using conventional mild hydrodesulfurization methods, at mildoperating conditions, i.e. hydrogen partial pressure of 10-30 kg/cm²,temperatures of 330-360° C., liquid hourly space velocity of 1-4 volumeof liquid per volume of catalysts and per hour. However, certain highlybranched aliphatic molecules can sterically hinder the sulfur atomremoval and are moderately more difficult (refractory) to desulfurizeusing conventional hydrodesulfurization methods.

Among the sulfur-containing aromatic compounds, thiophenes andbenzothiophenes are relatively easy to hydrodesulfurize. The addition ofalkyl groups to the ring compounds increases the difficulty ofhydrodesulfurization. Dibenzothiophenes resulting from addition ofanother aromatic ring to the benzothiophene family are even moredifficult to desulfurize, and the difficulty varies greatly according totheir alkyl substitution, with di-beta substitution being the mostdifficult to desulfurize, thus justifying their “refractory”appellation. These beta substituents hinder exposure of the heteroatomto the active site on the catalyst.

The economical removal of refractory sulfur-containing compounds istherefore exceedingly difficult to achieve, and accordingly removal ofsulfur-containing compounds in hydrocarbon fuels to an ultra-low sulfurlevel is very costly utilizing current hydrotreating techniques. Whenprevious regulations permitted sulfur levels up to 500 ppmw, there waslittle need or incentive to desulfurize beyond the capabilities ofconventional hydrodesulfurization, and hence the refractorysulfur-containing compounds were not targeted. However, in order to meetthe more stringent sulfur specifications, these refractorysulfur-containing compounds must be substantially removed fromhydrocarbon fuels streams.

The development of non-catalytic processes for desulfurization ofpetroleum distillate feedstocks has been widely studied, and certainapproaches are based on oxidation of sulfur-containing compoundsdescribed, e.g., in U.S. Pat. Nos. 5,910,440, 5,824,207, 5,753,102,3,341,448 and 2,749,284. Well known oxidizing agents include gaseousforms of oxygen, such as air or pure oxygen. In addition, it is known touse aqueous oxidant such as hydrogen peroxide, or organic peroxides, asoxidizing agents.

Organic peroxides are a very versatile source of active oxygen atoms andradicals. Radicals are formed after the thermally induced homolysis ofthe peroxide bond. The major radical-molecule reactions are additionsand homolytic bimolecular substitution reaction, e.g. H-abstraction,atom transfer, unimolecular reactions, e.g. decarboxylation, β-scissionand rearrangements, e.g. 1,5-H-abstraction. In synthesis reactions,undesired radical-radical reactions such as radical combination anddisproportionation can be avoided by proper choice of the type ofperoxide and reaction conditions. Another major application of organicperoxides in synthesis is oxidation, which is a non-radical reaction.

There are several important parameters for the selection of peroxide foruse in chemical reactions. Physical and chemical stability impacts thestorage and handling properties, and the temperature dependent rate ofdecomposition determines the reactivity at the process conditions.Decomposition products of the peroxides, therefore, must be taken inaccount during the purification process.

Organic peroxides are well established synthetic agents in themanufacture of many pharmaceutical intermediates, herbicides,insecticides and various other fine chemicals. Organic peroxides offeropportunities to reduce the number of reaction steps in synthetic routesapplying classical synthetic procedures.

Organic peroxides combine a number of interesting features for theirapplication in organic synthesis, including high purity, highefficiency, favorable solubility in most organic systems therebyenabling homogeneous reaction conditions, well defined and temperaturecontrolled reactivity, and favorable cost-to-performance ratios.

Organic peroxides can have a variety of characteristics depending ontheir chemical structure and reactivity. Reactivity of the peroxidesdepends on the peroxide group configuration and on the type ofsubstituent. Organic peroxides can be classified into different groupsdepending on their chemical structures, as shown in Table 2:

TABLE 2 Type of Peroxide Structure Hydroperoxide

Ketone peroxide

Peroxyacid

Dialkylperoxide R1—O—O—R2 Peroxyester

Peroxycarbonate

Diacylperoxide

Peroxydicarbonate

Cyclic ketone peroxide

Thermally induced homolysis of the peroxide bonds yield oxy-radicals.The decomposition rate of the peroxides not only depends on the class ofperoxide, but also on the type of R-group. Therefore, the reactivity andsensitivity of the peroxides to radical attack, i.e., induceddecomposition, is strongly dependent upon its structure.

The thermal decomposition of organic peroxides is a first orderreaction. Increase in temperature of about 10° C. results in a 2-3 foldincrease in decomposition rate. The decomposition is further acceleratedwith catalysts possessing high oxidation potential. The half-life timesof various organic peroxides varies from 0.1 to 10 hours on a range oftemperature from 70° C. to 210° C.

Organic peroxides are commonly associated with safety hazards duringexperimental preparation and synthesis, storage and transportation.Thus, heightened safety precautions and measures are required whenhandling organic peroxides. Known safety measures include, cooling theorganic peroxides to low temperatures, preparing the organic peroxidesin a diluted medium such as water, and/or incorporation of chemicalstabilizers. These precautions are necessary to minimize the likelihoodof impact shock and thermal influence caused by exothermic reactions.

It would be desirable to provide an oxidative process for convertingheteroatoms into their corresponding oxidation products that minimizesthe need for safety measures required for handling of organic peroxides.

SUMMARY OF THE INVENTION

An oxidative treatment process, e.g., oxidative desulfurization ordenitrification, is provided in which the oxidant is produced in-situusing an aromatic-rich portion of the original liquid hydrocarbonfeedstock. The process reduces or replaces the need for the separateintroduction of liquid oxidants such as hydrogen peroxide, organicperoxide and organic hydroperoxide in an oxidative treatment process.

In accordance with one or more embodiments, a process for conversion ofheteroatom-containing compounds in a hydrocarbon feedstock to theiroxidation products is provided. The hydrocarbon feedstock is separatedinto an aromatic-lean fraction and an aromatic-rich fraction. Thearomatic-rich fraction is contacted with an effective amount of gaseousoxidant under conditions effective for organic peroxide generation andto produce a mixture containing organic peroxide andheteroatom-containing hydrocarbons. The mixture containing producedorganic peroxide and heteroatom-containing hydrocarbons is contactedwith the aromatic-lean fraction under conditions effective for oxidativeconversion of heteroatom-containing hydrocarbons in the mixture and inthe aromatic-lean fraction into oxidation products ofheteroatom-containing hydrocarbons.

In accordance with one or more additional embodiments, a process isprovided for conversion of heteroatom-containing compounds in ahydrocarbon feedstock to their oxidation products. The hydrocarbonfeedstock is separated into an aromatic-lean fraction and anaromatic-rich fraction. The aromatic-rich fraction is contacted with aneffective amount of gaseous oxidant under conditions effective fororganic peroxide generation and to produce a mixture containing organicperoxide and heteroatom-containing hydrocarbons. All or a portion of thearomatic-lean fraction is hydrotreated. The mixture containing producedorganic peroxide and heteroatom-containing hydrocarbons is retainedunder conditions effective for oxidative conversion ofheteroatom-containing hydrocarbons into oxidation products of theheteroatom-containing hydrocarbons.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments of the invention will be best understood when readin conjunction with the attached drawings, in which like referencenumerals represent similar elements or operations. For the purpose ofillustrating the invention, there are shown in the drawings embodimentswhich are presently preferred. It should be understood, however, thatthe invention is not limited to the precise arrangements and apparatusshown, in which:

FIG. 1 is a process flow diagram of an integrated process for in-situgeneration of organic peroxides and oxidation;

FIG. 2 illustrates a chemical reaction route for oxidation via peroxycompounds.

FIG. 3 is a process flow diagram of another embodiment of an integratedprocess for in-situ generation of organic peroxides and oxidation of anaromatic-rich portion, and hydrotreating of an aromatic-lean portion;

FIG. 4 is a process flow diagram of a further embodiment of anintegrated process for in-situ generation of organic peroxides andoxidation of an aromatic-rich portion, and hydrotreating of anaromatic-lean portion, in which generation of organic peroxides andoxidation occur in a common apparatus or vessel;

FIG. 5 is a process flow diagram of solvent handling for an aromaticseparation apparatus;

FIGS. 6-11 show various examples of apparatus suitable for use as thearomatic separation apparatus;

FIG. 12A is the chemical structure of a Co(Salophen) used as a catalystfor organic peroxide generation in the example herewith; and

FIG. 12B is a gas chromatography chart depicting cumene peroxideformation in the example herewith.

DETAILED DESCRIPTION OF THE INVENTION

A system and process is provided for conversion of sulfur-containing andnitrogen-containing hydrocarbon compounds to their respective oxidationproducts by oxidation using in-situ generated peroxides. In-situgenerated peroxides compounds are produced from the hydrocarbonfeedstock by reacting an aromatic-rich fraction derived from theinfluent feedstock with one or more gaseous oxidants. The resultantperoxides are used as selective oxidants for conversion ofsulfur-containing and nitrogen-containing hydrocarbon compounds to theirrespective oxidation products, thereby eliminating the requisitetransportation, storage and handling expenses conventionally associatedwith organic peroxides. The oxidation products can be removed by knownextraction and/or adsorption processes to produce hydrocarbon productshaving reduced concentrations of sulfur-containing andnitrogen-containing hydrocarbon mixtures suitable for use as fuels orrefinery feedstocks.

Referring to FIG. 1, an oxidative desulfurization system 10 is shownthat generally includes an optional feed separation apparatus 12, anaromatic separation apparatus 14, an organic peroxide generationapparatus 16, an oxidative reaction apparatus 18 and an oxidationproduct separation apparatus 20.

Feed separation apparatus 12 can be optional as denoted by dashed linesin FIG. 1, and is any suitable apparatus to partition the initialfeedstock. It can be a simple diverter to provide a slipstream of afeedstream, a flash separation apparatus to fraction a feedstream basedon a temperature cup point, or a distillation unit. In general, feedseparation apparatus 12 includes an inlet for receiving a feedstream 22and plural outlets for discharging streams 22 a and 22 b (optional asdenoted by dashed lines in FIG. 1).

Aromatic separation apparatus 14 generally includes an inlet forreceiving stream 22 a of feedstock 22 (or the entire feedstock 22 inembodiments in which feed separation apparatus is not employed), anaromatic-rich outlet for discharging an aromatic-rich stream 24 and anaromatic-lean outlet for discharging an aromatic-lean stream 26.

Organic peroxide generation apparatus 16 includes an aromatic-rich inletfor receiving aromatic-rich stream 24, a gas inlet for receiving agaseous oxidant stream 28, and an oxidant outlet for discharging aneffluent 32 including organic peroxide and any unreacted, unconverted orpartially converted hydrocarbons and heteroatom-containing hydrocarbonsincluding organosulfur and organonitrogen compounds. In certainembodiments, apparatus 16 contains an effective quantity ofheterogeneous catalyst to promote organic peroxide generation. Inalternative embodiments (as indicated in FIG. 1 with dashed lines), orin combination with an effective quantity of heterogeneous catalyst,apparatus 16 includes an inlet for receiving an effective quantity ofhomogeneous catalyst via stream 30.

In additional embodiments (not shown), gaseous oxidant and/orhomogeneous catalyst (in embodiments in which homogeneous catalyst isprovided) can be mixed with aromatic-rich stream 24, and the combinedfeed charged to organic peroxide generation apparatus 16.

In certain embodiments, shown in broken lines in FIG. 1, a mixer can beprovided upstream of apparatus 16 in which gaseous oxidant, thearomatic-rich fraction, and homogeneous catalyst are admixed prior topassage into organic peroxide generation apparatus 16.

Oxidative reaction apparatus 18 generally includes an inlet forreceiving stream 22 b of feedstock 22 (in embodiments in which feedseparation apparatus 12 is employed), aromatic-lean stream 26 andorganic peroxide stream 32 from organic peroxide generation apparatus16. In addition, oxidative reaction apparatus 18 includes an outlet fordischarging a hydrocarbon stream 36 containing oxidizedsulfur-containing and nitrogen-containing compounds. In certainembodiments, apparatus 18 contains an effective quantity ofheterogeneous catalyst to promote oxidative desulfurization. Inalternative embodiments (as indicated in FIG. 1 with dashed lines), orin combination with an effective quantity of heterogeneous catalyst,apparatus 18 includes an inlet for receiving an effective quantity ofhomogeneous catalyst 34.

In additional embodiments (not shown), homogeneous catalyst (inembodiments in which homogeneous catalyst is provided) can be mixed witharomatic-lean stream 26, or in embodiments in which feed separationapparatus 12 is included, partitioned stream 22 b or the combined streampartitioned stream 22 b and aromatic-lean stream 26. Thecatalyst-containing feed is then charged to oxidation reaction apparatus18.

Oxidation product separation apparatus 20 contains an inlet forreceiving oxidized hydrocarbon stream 36, an outlet for discharging ahydrocarbon product stream 38 and an outlet for discharging a stream 40containing concentrated oxidation products of sulfur-containing andnitrogen-containing hydrocarbon compounds.

In operation of system 10, the hydrocarbon feed stream 22 to be treatedcan be divided into portions 22 a, 22 b, in which only partial stream 22a is subjected to the aromatic separation apparatus 16. In embodimentsin which feed separation apparatus 12 is not deployed, the entire feedstream 22 is passed to the aromatic separation.

In embodiments in which feed separation apparatus 12 is a simplediverter, partial stream 22 a is a slipstream of the initial feed 22.

In other embodiments in which feed separation apparatus 12 is a flash ordistillation unit, partial stream 22 a contains hydrocarbons having aboiling point at or above a certain temperature cut point, and partialstream 22 b contains hydrocarbons having a boiling point below thetemperature cut point. For instance, a substantial portion of thearomatic content in a feed suitable for use in the present process has aboiling point at or above about 300° C. to about 360° C., and in certainembodiments at or above about 340° C.

Feedstock 22 or partial stream 22 a is fractioned into aromatic-richstream 24 and aromatic-lean stream 26 in separation apparatus 14.Aromatic-rich stream 24 and gaseous oxidant stream 28, and optionallyhomogeneous catalyst 30, are introduced to organic peroxide generationapparatus 16. Gaseous oxidants suitable for peroxide generation include,but are not limited to oxides of nitrogen (e.g., nitrous oxide), oxygen,air, ozone, or combinations comprising any of these gaseous oxidants.The contents are maintained in organic peroxide generation apparatus 16under suitable operating conditions and for a residence time sufficientto produce a desired quantity of organic peroxide.

Peroxy acids are often used for the epoxidation of unsaturatedcompounds. The Baeyer-Villiger reaction of carbonyl compounds isnotable, in which oxidation of nitrogen and sulfur compounds occurs asshown in FIG. 2.

According to the process herein, organic peroxides generated in organicperoxide generation apparatus 16 can be well-known compounds, most ofwhich are otherwise available from commercial sources, but in thosecases subject to transportation and handling costs.

The in-situ generated organic peroxides are of the general formulaR′—OOR, wherein R represents an organic group containing one aromatic ormulti-ring aromatics or naphtheno-aromatics substituted with one orseveral alkyl groups that have exposed tertiary hydrogen readilysusceptible to oxidation, and wherein R′ represents any of the compoundsof R or hydrogen.

In particular, the reaction path for generation of organic peroxides isshown in the below equations (1)-(4), wherein M is the catalyst:

In the above equations (1)-(4), Equations (1)-(2) provide for generationof radicals. Equation (3) provides for peroxy radical formation.Equation (4) shows the chain reaction of the peroxide radical reactingwith additional hydrocarbons to generate additional radicals. Asdiscussed above, with respect to the general formula R′—OOR, Rrepresents an organic group containing one aromatic or multi-ringaromatics or naphtheno-aromatics substituted with one or several alkylgroups that have exposed tertiary hydrogen readily susceptible tooxidation. In the case of equations (1)-(4), R′ is hydrogen.

By separating the compounds that are easily oxidized to form peroxides,including aromatics and certain naphthenes, particularly thosecontaining tertiary carbon, both in-situ generation of peroxidesoxidative desulfurization can occur under relatively milder conditions.

It is noted that, although in certain existing oxidative desulfurizationoperations gaseous oxidant can be directly used to convert organosulfurcompounds to their oxidation products, the gaseous oxidant in theseexisting processes are generally less selective as compared to usingorganic peroxide as described herein, and also requires relatively moresevere operating conditions.

Aromatic-lean stream 26 from aromatic separation apparatus 14, partialstream 22 b (in embodiments in which feed separation apparatus 12 isemployed), and stream 32 that is discharged from organic peroxidegeneration apparatus 16, which contains the newly formed organicperoxide compounds as well as unconverted aromatics compounds andnaphthenic compounds from the feed to organic peroxide generationapparatus 16, are charged to oxidative reaction apparatus 18, optionallyalong with homogeneous catalyst via stream 34.

The contents are maintained in oxidative reaction apparatus 18 undersuitable operating conditions and for a residence time sufficient topromote the desired oxidation reactions, i.e., oxidative conversion ofsulfur-containing hydrocarbons to those containing sulfur and oxygen,such as sulfoxides or sulfones, and the nitrogen-containing hydrocarbonscompounds to those containing nitrogen and oxygen.

In order to produce a hydrocarbon product having reduced levels ofsulfur-containing and nitrogen-containing hydrocarbon compounds, stream36, containing non-heteroatom hydrocarbons and oxidation products ofsulfur-containing and nitrogen-containing hydrocarbon compounds, isconveyed from oxidative reaction apparatus 18 to oxidation productseparation apparatus 20. This separation step can include, for instance,one or more of polishing, extraction, adsorption or decantation. Ahydrocarbon product stream 38 having reduced levels of sulfur-containingand nitrogen-containing hydrocarbon compounds is discharged from theoxidation product separation apparatus 20. A stream 40 containingconcentrated oxidation products of sulfur-containing andnitrogen-containing hydrocarbon compounds is also discharged, which canbe subjected to further processing to recover hydrocarbons such as FCC,hydroprocessing, coker, visbreaker, or incorporated into a heavy gas oilpool.

FIGS. 3 and 4 show additional embodiments in which a hydrotreating unitis integrated to treat the aromatic-lean fraction. While the descriptionrefers to the entire aromatic-lean fraction, it is to be appreciatedthat a portion of the aromatic-lean fraction can be subjected tooxidative desulfurization reactions, e.g., as shown and described withrespect to FIG. 1.

Referring now to FIG. 3, a system 110 is depicted including anarrangement of unit operations suitable for another embodiment of aprocess incorporating in-situ generation of organic peroxide oxidants isprovided. The arrangement and operation of an organic peroxidegeneration apparatus 116, an oxidative reaction apparatus 118 and anoxidation products separation apparatus 120 are similar to that oforganic peroxide reaction apparatus 16, oxidative reaction apparatus 18and oxidation products separation apparatus 20 as discussed above withreference to FIG. 1. In system 110, an aromatic separation apparatus 114is provided which separates aromatic contents from an initial feedstream122 into an aromatic-rich stream 124 and an aromatic-lean stream 126.Aromatic-rich stream 124 can be separated into a partial stream 124 aand 124 b in an aromatic-rich stream separation apparatus 172 prior tobeing passed to the organic peroxide generation apparatus 116.Aromatic-rich stream separation apparatus 172, an optional unitoperation as denoted by dashed lines in FIG. 3, can be any suitableapparatus to partition aromatic-rich stream 124. Similar to the initialfeed separation apparatus 12 described with respect to FIG. 1, apparatus172 can be a simple diverter to provide a slipstream of aromatic-richstream 124, a flash separation apparatus to fraction aromatic-richstream 124 based on a temperature cup point, or a distillation unit.

A generated organic peroxide selective oxidant stream 132 is conveyed tooxidative reaction apparatus 118, optionally along with partial stream124 b in embodiments in which aromatic-rich stream separation apparatus172 is employed, and optionally with homogeneous catalyst via stream 134either as the sole source of catalyst or in combination withheterogeneous catalyst contained in oxidative reaction apparatus 118.

The contents are maintained in oxidative reaction apparatus 118 undersuitable operating conditions and for a residence time sufficient topromote the desired oxidation reactions. A stream 136, containingnon-heteroatom hydrocarbons and oxidation products of sulfur-containingand nitrogen-containing hydrocarbon compounds, is conveyed fromoxidative reaction apparatus 118 to oxidation products separationapparatus 120, from which an aromatic-rich hydrocarbon product stream138 having reduced levels of sulfur-containing and nitrogen-containinghydrocarbon compounds is discharged along with a stream 140 containingconcentrated oxidation products of sulfur-containing andnitrogen-containing hydrocarbon compounds.

The aromatic-lean stream 126 from the aromatic separation apparatus 114is conveyed, along with hydrogen via a stream 166, to a hydrotreatingapparatus 164. In certain embodiments, all or a portion of thehydrocarbon product stream 138 from the oxidation products separationapparatus 120, stream 174, can also be conveyed to the hydrotreatingapparatus 164 for further desulfurization and/or denitrification.

Desulfurized and/or denitrified products from hydrotreating apparatus164 can be discharged separately as an aromatic-lean hydrotreatedproduct via a stream 168, or optionally combined with the hydrocarbonproduct stream 138 as a stream 170. The product stream(s) can be passedto further refining operations or used/delivered as end product.

Referring now to FIG. 4, a system 210 is depicted including anarrangement of unit operations suitable for another embodiment of aprocess incorporating in-situ generation of organic peroxide oxidants isprovided. The arrangement and operation of unit operations in system 210are similar to that of system 110 as discussed above with reference toFIG. 3, with a modification whereby organic peroxide generation andoxidative reactions occur in a common reactor 217. In this embodiment,an optional homogeneous catalyst stream 233 can be conveyed to reactor217 either as the sole source of catalyst or in combination withheterogeneous catalyst contained in reactor 217. Either or both of thehomogeneous catalyst stream 233 or a heterogeneous catalyst contained inreactor 217 can be a bi-functional catalyst suitable for promotingorganic peroxide generation from an aromatic-rich stream 224 and forpromoting oxidative reaction of the heteroatom-containing hydrocarboncompounds, e.g., desulfurization.

Note that while the dual function vessel is shown in a configurationwith the mild hydrotreatment zone, it is intended that this dualfunction vessel can be utilized in a system similar to that shown withrespect to FIG. 1, i.e., in which removal of heteroatoms occurs entirelyby oxidative reactions.

The hydrocarbon feed stream to be treated according to the processherein is generally a liquid hydrocarbon stream, such as straight runfuel oil or diesel, which includes sulfur-containing andnitrogen-containing hydrocarbon compounds. Hydrocarbon feedstockssuitable for reduction of heteroatom-containing compounds by the systemand process of the present invention can include hydrocarbon fractionsboiling in the range of about 36° C. to about 520° C., preferably about36° C. to about 370° C. The sulfur-containing compounds that canadvantageously be removed include mercaptans, thiophenic compounds,benzothiophenic compounds and dibenzothiophenic compounds, which caninclude substituted alkyl, aryl or alkaryl groups. Thenitrogen-containing compounds that can advantageously be removed includepyridines, amines, pyrroles, anilines, quinolines, and acridines, whichcan include substituted alkyl, aryl or alkaryl groups. In particular,feedstocks containing one or more benzothiophenic compounds,dibenzothiophenic compounds, pyrroles, quinolines or acridines canbenefit from the process described herein, as these compounds aretypically not removable by hydrotreating under relatively mildconditions.

In embodiments in which a feed or aromatic rich separation apparatus 12,172 is provided and is a simple diverter, stream 22 a, 124 a can includeabout 1 V % to about 90 V % of the influent stream 22, 124, in certainembodiments about 1 V % to about 50 V %, and in further embodimentsabout 1 V % to about 30 V %. In embodiments in which feed separationapparatus 12, 172 is provided and is a flash or distillation apparatus,a stream 22 a, 124 a, with an initial boiling point in the range ofabout 300° C. to about 360° C. and in certain embodiments in the rangeof about 300° C. to about 360° C., can include about 1 V % to about 50 V% of the influent stream 22, 124 in certain embodiments about 1 V % toabout 30 V %, and in further embodiments about 1 V % to about 5 V %

The proportions of the aromatic-rich fraction and the aromatic-leanfraction are primarily dependant on the type of aromatic separationapparatus employed. In addition, in embodiments of system 10, theseproportions also can depend on whether feed separation apparatus 12 is adiverter or based on a flash or distillation separation. Due to natureof aromatic separation processes such as solvent extraction, theextracted aromatics fraction will contain non-aromatic compounds,including naphtenes and paraffins.

Since aromatic extraction operations typically do not provide sharpcut-offs between the aromatics and non-aromatics, the aromatic-leanfraction contains a major proportion of the non-aromatic content of theinitial feed and a minor proportion of the aromatic content of theinitial feed, and the aromatic-rich fraction contains a major proportionof the aromatic content of the initial feed and a minor proportion ofthe non-aromatic content of the initial feed. The amount ofnon-aromatics in the aromatic-rich fraction, and the amount of aromaticsin the aromatic-lean fraction, depend on various factors as will beapparent to one of ordinary skill in the art, including the type ofextraction and the number of theoretical plates in the extractor, thetype of solvent and the solvent ratio.

The aromatic compounds that pass to the aromatic-rich fraction includearomatic organosulfur compounds, such as benzothiophene,dibenzothiophene, benzonaphtenothiophene, and derivatives ofbenzothiophene, dibenzothiophene and benzonaphtenothiophene. Variousnon-aromatic organosulfur compounds that may have been present in theinitial feed, i.e., prior to hydrotreating, include mercaptans, sulfidesand disulfides.

In addition, certain organonitrogen compounds having aromatic moietiesalso pass with the aromatic-rich fraction. Further, certain organicnitrogen compounds, paraffinic or naphthenic nature, may have polaritiescausing them to be extracted and remain in aromatic-rich fraction.

As used herein, the term “aromatic-lean” means at least greater than 50wt % of the non-aromatic content of the feed to the aromatic separationapparatus, preferably at least greater than about 85 wt %, and mostpreferably greater than at least about 95 wt %. Also as used herein, theterm “aromatic-rich” means at least greater than 50 wt % of the aromaticcontent of the feed to the aromatic separation apparatus, preferably atleast greater than about 85 wt %, and most preferably greater than atleast about 95 wt %.

In embodiments of the present invention, the organic peroxide generationapparatus includes one or more types of continuous flow or batchreactors including but not limited to a continuous stirred-tankreactors, fixed-bed, continuous stirred fixed bed reactors,ebullated-bed, slurry bed, moving bed, or bubble column.

Suitable catalysts employed in the organic peroxide generation apparatusinclude but are not limited to those having the general formulaM_(x)O_(y), where x=1 or 2, and y=2 or 5, and where M is an element thatis selected from the group consisting of the elements of groups IVB, VBand VIB of the Periodic Table or/an a mixture of thereof. Examples ofsuitable peroxide generation catalyst active components include, but arenot limited to, complex metals of Ni, Ti, Zr, Cr, Mo and or W in therange of 5 ppm to 1 wt. %. Examples of particular peroxide generationcatalyst compounds include, but are not limited to, MoO₂, Fe₂O₃, V₂O₅,ZrO₂, and TiO₂. In additional embodiments, suitable catalysts employedin the organic peroxide generation apparatus include Co(Salophen) or itscomplexes, and example of which is shown in FIG. 12A.

In additional embodiments, as noted above, homogeneous catalysts can beused in place of, or in conjunction with, heterogeneous catalysts in theorganic peroxide generation apparatus. Suitable homogeneous catalystsfor peroxide oxidant generation include transition metal complexes.

In the organic peroxide generation apparatus, the aromatic-rich feed ismaintained in contact with the gaseous oxidant and catalyst for asufficient period of time to complete organic peroxides generation,generally about 5 minutes to about 180 minutes, in certain embodimentsabout 15 minutes to about 90 minutes and in further embodiments at about30 minutes to about 60 minutes.

The reaction conditions of the organic peroxide generation apparatusinclude an operating pressure of about 1 bar to about 30 bars, incertain embodiments about 1 bar to about 10 bars and in furtherembodiments at about 1 bar to about 3 bars; and an operating temperatureof about 20° C. to about 300° C., in certain embodiments about 20° C. toabout 150° C. and in further embodiments about 45° C. to about 60° C.

The molar feed ratio of gaseous oxidant to aromatic carbon is generallyabout 1:1 to about 100:1, in certain embodiments about 1:1 to about30:1, and in further embodiments about 1:1 to about 4:1.

The quantity of organic peroxide produced in the organic peroxidegeneration apparatus can be about 0.1 V % to about 30 V % in certainembodiments about 0.1 V % to about 10 V % and in further embodimentsabout 0.1 V % to about 5 V %.

In embodiments of the present invention, oxidative reaction apparatusincludes one or more types of continuous flow or batch reactorsincluding but not limited to continuous stirred-tank reactors,fixed-bed, continuous stirred fixed bed reactors, ebullated-bed, slurrybed, moving bed, or bubble column.

Suitable catalysts can also be employed in the oxidative reactionapparatus, including but not limited to alkali transition metal oxides.For instance, the oxidation catalyst can be selected from one or morehomogeneous or heterogeneous catalysts having metals from Group VB toGroup VIIIB of the Periodic Table, including those selected from Mn, Co,Fe, Cr Ni, Ti, Zr, W, V and Mo. Examples of suitable oxidation catalystcompounds include molybdenum hexacarbonyl, molybdenum acetylacetone,MoO₂, Fe₂O₃, V₂O₅, ZrO₂, TiO₂. In additional embodiments, the oxidativereaction catalyst includes salts of transition metal oxides, whereinsalts are selected from Group IA and IIA of the Periodic Table such asNa⁺, K⁺, Ca²⁺, Mg²⁺, or mixtures thereof, including but not limited tosodium tungstate.

In addition, one or more phase transfer agents, such as formic or aceticacid can be included with the oxidative reaction mixture.

The oxidative reactions can be carried out in the oxidative reactionapparatus at an operating pressure of about 1 bar to about 30 bars, incertain embodiments about 1 bar to about 10 bars and in furtherembodiments at about 1 bar to about 3 bars; and an operating temperatureof about 20° C. to about 300° C., in certain embodiments about 20° C. toabout 150° C. and in further embodiments about 45° C. to about 60° C.The molar feed ratio of oxidizing agent to sulfur is generally about 1:1to about 100:1, in certain embodiments about 1:1 to about 30:1, and infurther embodiments about 1:1 to about 4:1, residence time about 5 toabout 180 minutes, in certain embodiments about 15 to about 90 minutesand in further embodiments about 15 minutes to about 30 minutes.

In embodiments of the present invention, oxidation product separationapparatus 20 includes one or more unit operations including but notlimited to decanting vessels, distillation units, adsorption units, orsolvent extraction units. The details and specific arrangement ofoxidation product separation apparatus 20 are beyond the scope of thepresent description.

In certain embodiments, for instance as described with respect to FIG.4, bi-functional catalyst compounds are provided, containing one or moremetal active species to catalytically promote peroxide generation andone or more metal active species to promote oxidation ofheteroatom-containing hydrocarbon compounds reactions. Suitablebi-functional homogeneous catalyst compounds that can be used insteadof, or in conjunction with, heterogeneous catalyst include, but are notlimited to those derived from combinations of metal naphthenate or metalacetate of metals from groups IIB to IVB such as Cu(acac)2-VO(acac)2; orCu(acac)2-Co(acac)2.

In a combined reaction apparatus for organic peroxide generation andoxidative reaction, the aromatic-rich feed is maintained in contact withthe gaseous oxidant and catalyst for a sufficient period of time tocomplete organic peroxides generation and oxidative reaction, generallyabout 5 to about 180 minutes, in certain embodiments about 15 to about90 minutes and in further embodiments about 15 minutes to about 30minutes.

The reaction conditions of the organic peroxide generation apparatusinclude an operating temperature of about 25° C. to about 300° C., incertain embodiments about 25° C. to about 250° C. and in furtherembodiments about 25° C. to about 200° C. The reaction conditions of theorganic peroxide generation apparatus include an operating pressure ofabout 1 bars to about 50 bars, in certain embodiments about 1 bar toabout 40 bars and in further embodiments at about 1 bar to about 30bars;

Suitable apparatus for a dual function reactor include one or more typesof continuous flow or batch reactors including but not limited to acontinuous stirred-tank reactors, fixed-bed, continuous stirred fixedbed reactors, ebullated-bed, slurry bed, moving bed, or bubble column.

The aromatic separation apparatus used herein can be a suitable solventextraction aromatic separation apparatus capable of partitioning thefeed thereto into aromatic-lean stream and aromatic-rich stream. Asshown in FIG. 5, an aromatic separation apparatus 314 can includesuitable unit operations to perform a solvent extraction of aromatics,and recover solvents for reuse in the process. A feed 322 is conveyed toan aromatic extraction vessel 344 in which a first, aromatic-lean,fraction is separated as a raffinate stream 346 from a second, generallyaromatic-rich, fraction as an extract stream 348. A solvent feed 350 isintroduced into the aromatic extraction vessel 344.

In operations in which the solvent existing in stream 346 exceeds adesired or predetermined amount, solvent can be removed from thehydrocarbon product, for example, using a flashing or stripping unit352, or other suitable apparatus. Solvent 354 from the flashing unit 352can be recycled to the aromatic extraction vessel 344, e.g., via a surgedrum 356. Initial solvent feed or make-up solvent can be introduced viastream 362. An aromatic-lean stream 326 is discharged from the flashingunit 352 and conveyed to the oxidative reaction apparatus 318 asdescribed above.

In addition, where solvent existing in stream 348 exceeds a desired orpredetermined amount, solvent can be removed from the hydrocarbonproduct, for example, using a flashing or stripping unit 358 or othersuitable apparatus. Solvent 60 from the flashing unit 354 can berecycled to the aromatic extraction vessel 344, e.g., via the surge drum356. An aromatic-rich stream 324 is discharged from the flashing unit358.

Selection of solvent, operating conditions, and the mechanism ofcontacting the solvent and feed permit control over the level ofaromatic extraction. For instance, suitable solvents include furfural,N-methyl-2-pyrrolidone, dimethylformamide or dimethylsulfoxide, and canbe provided in a solvent to oil ratio of about 20:1, in certainembodiments about 4:1, and in further embodiments about 1:1. Thearomatic separation apparatus can operate at a temperature in the rangeof about 20° C. to about 120° C., and in certain embodiments in therange of about 40° C. to about 80° C. The operating pressure of thearomatic separation apparatus can be in the range of about 1 bar toabout 10 bars, and in certain embodiments, in the range of about 1 barto 3 bars. Types of apparatus useful as the aromatic separationapparatus of the present invention include stage-type extractors ordifferential extractors.

An example of a stage-type extractor is a mixer-settler apparatus 414schematically illustrated in FIG. 6. Mixer-settler apparatus 414includes a vertical tank 480 incorporating a turbine or a propelleragitator 482 and one or more baffles 484. Charging inlets 486, 488 arelocated at the top of tank 480 and outlet 490 is located at the bottomof tank 480. The feedstock to be extracted is charged into vessel 480via inlet 486 and a suitable quantity of solvent is added via inlet 488.The agitator 482 is activated for a period of time sufficient to causeintimate mixing of the solvent and charge stock, and at the conclusionof a mixing cycle, agitation is halted and, by control of a valve 492,at least a portion of the contents are discharged and passed to asettler 494. The phases separate in the settler 494 and a raffinatephase containing an aromatic-lean hydrocarbon mixture and an extractphase containing an aromatic-rich mixture are withdrawn via outlets 496and 498, respectively. In general, a mixer-settler apparatus can be usedin batch mode, or a plurality of mixer-settler apparatus can be stagedto operate in a continuous mode.

Another stage-type extractor is a centrifugal contactor. Centrifugalcontactors are high-speed, rotary machines characterized by relativelylow residence time. The number of stages in a centrifugal device isusually one, however, centrifugal contactors with multiple stages canalso be used. Centrifugal contactors utilize mechanical devices toagitate the mixture to increase the interfacial area and decrease themass transfer resistance.

Various types of differential extractors (also known as “continuouscontact extractors,”) that are also suitable for use as an aromaticextraction apparatus in zone 22 of the present invention include, butare not limited to, centrifugal contactors and contacting columns suchas tray columns, spray columns, packed towers, rotating disc contactorsand pulse columns.

Contacting columns are suitable for various liquid-liquid extractionoperations. Packing, trays, spray or other droplet-formation mechanismsor other apparatus are used to increase the surface area in which thetwo liquid phases (i.e., a solvent phase and a hydrocarbon phase)contact, which also increases the effective length of the flow path. Incolumn extractors, the phase with the lower viscosity is typicallyselected as the continuous phase, which, in the case of an aromaticextraction apparatus, is the solvent phase. In certain embodiments, thephase with the higher flow rate can be dispersed to create moreinterfacial area and turbulence. This is accomplished by selecting anappropriate material of construction with the desired wettingcharacteristics. In general, aqueous phases wet metal surfaces andorganic phases wet non-metallic surfaces. Changes in flows and physicalproperties along the length of an extractor can also be considered inselecting the type of extractor and/or the specific configuration,materials or construction, and packing material type and characteristics(i.e., average particle size, shape, density, surface area, and thelike).

A tray column 514 is schematically illustrated in FIG. 7. A light liquidinlet 588 at the bottom of column 514 receives liquid hydrocarbon, and aheavy liquid inlet 590 at the top of column 514 receives liquid solvent.Column 514 includes a plurality of trays 580 and associated downcomers582. A top level baffle 584 physically separates incoming solvent fromthe liquid hydrocarbon that has been subjected to prior extractionstages in the column 514. Tray column 514 is a multi-stagecounter-current contactor. Axial mixing of the continuous solvent phaseoccurs at region 586 between trays 580, and dispersion occurs at eachtray 580 resulting in effective mass transfer of solute into the solventphase. Trays 580 can be sieve plates having perforations ranging fromabout 1.5 to 4.5 mm in diameter and can be spaced apart by about 150-600mm.

Light hydrocarbon liquid passes through the perforation in each tray 580and emerges in the form of fine droplets. The fine hydrocarbon dropletsrise through the continuous solvent phase and coalesce into an interfacelayer 596 and are again dispersed through the tray 580 above. Solventpasses across each plate and flows downward from tray 580 above to thetray 580 below via downcomer 582. The principle interface 598 ismaintained at the top of column 514. Aromatic-lean hydrocarbon liquid isremoved from outlet 592 at the top of column 514 and aromatic-richsolvent liquid is discharged through outlet 594 at the bottom of column514. Tray columns are efficient solvent transfer apparatus and havedesirable liquid handling capacity and extraction efficiency,particularly for systems of low-interfacial tension.

An additional type of unit operation suitable for extracting aromaticsfrom the hydrocarbon feed is a packed bed column. FIG. 8 is a schematicillustration of a packed bed column 614 having a hydrocarbon inlet 690and a solvent inlet 692. A packing region 688 is provided upon a supportplate 686. Packing region 688 comprises suitable packing materialincluding, but not limited to, Pall rings, Raschig rings, Kascade rings,Intalox saddles, Berl saddles, super Intalox saddles, super Berlsaddles, Demister pads, mist eliminators, telerrettes, carbon graphiterandom packing, other types of saddles, and the like, includingcombinations of one or more of these packing materials. The packingmaterial is selected so that it is fully wetted by the continuoussolvent phase. The solvent introduced via inlet 692 at a level above thetop of the packing region 688 flows downward and wets the packingmaterial and fills a large portion of void space in the packing region688. Remaining void space is filled with droplets of the hydrocarbonliquid which rise through the continuous solvent phase and coalesce toform the liquid-liquid interface 698 at the top of the packed bed column614. Aromatic-lean hydrocarbon liquid is removed from outlet 694 at thetop of column 614 and aromatic-rich solvent liquid is discharged throughoutlet 696 at the bottom of column 614. Packing material provides largeinterfacial areas for phase contacting, causing the droplets to coalesceand reform. The mass transfer rate in packed towers can be relativelyhigh because the packing material lowers the recirculation of thecontinuous phase.

Further types of apparatus suitable for aromatic extraction in thesystem and method of the present invention include rotating disccontactors. FIG. 9 is a schematic illustration of a rotating disccontactor 714 known as a Scheiebel® column commercially available fromKoch Modular Process Systems, LLC of Paramus, N.J., USA. It will beappreciated by those of ordinary skill in the art that other types ofrotating disc contactors can be implemented as an aromatic extractionunit included in the system and method of the present invention,including but not limited to Oldshue-Rushton columns, and Kuhniextractors. The rotating disc contactor is a mechanically agitated,counter-current extractor. Agitation is provided by a rotating discmechanism, which typically runs at much higher speeds than a turbinetype impeller as described with respect to FIG. 6.

Rotating disc contactor 714 includes a hydrocarbon inlet 790 toward thebottom of the column and a solvent inlet 792 proximate the top of thecolumn, and is divided into number of compartments formed by a series ofinner stator rings 782 and outer stator rings 784. Each compartmentcontains a centrally located, horizontal rotor disc 786 connected to arotating shaft 788 that creates a high degree of turbulence inside thecolumn. The diameter of the rotor disc 786 is slightly less than theopening in the inner stator rings 782. Typically, the disc diameter is33-66% of the column diameter. The disc disperses the liquid and forcesit outward toward the vessel wall 798 where the outer stator rings 784create quiet zones where the two phases can separate. Aromatic-leanhydrocarbon liquid is removed from outlet 794 at the top of column 714and aromatic-rich solvent liquid is discharged through outlet 796 at thebottom of column 714. Rotating disc contactors advantageously providerelatively high efficiency and capacity and have relatively lowoperating costs.

An additional type of apparatus suitable for aromatic extraction in thesystem and method of the present invention is a pulse column. FIG. 10 isa schematic illustration of a pulse column system 814, which includes acolumn with a plurality of packing or sieve plates 888, a light phase,i.e., solvent, inlet 890, a heavy phase, i.e., hydrocarbon feed, inlet892, a light phase outlet 894 and a heavy phase outlet 896.

In general, pulse column system 814 is a vertical column with a largenumber of sieve plates 888 lacking down corners. The perforations in thesieve plates 888 typically are smaller than those of non-pulsatingcolumns, e.g., about 1.5 mm to about 3.0 mm in diameter.

A pulse-producing device 898, such as a reciprocating pump, pulses thecontents of the column at frequent intervals. The rapid reciprocatingmotion, of relatively small amplitude, is superimposed on the usual flowof the liquid phases. Bellows or diaphragms formed of coated steel(e.g., coated with polytetrafluoroethylene), or any other reciprocating,pulsating mechanism can be used. A pulse amplitude of 5-25 mm isgenerally recommended with a frequency of 100-260 cycles per minute. Thepulsation causes the light liquid (solvent) to be dispersed into theheavy phase (oil) on the upward stroke and heavy liquid phase to jetinto the light phase on the downward stroke. The column has no movingparts, low axial mixing, and high extraction efficiency.

A pulse column typically requires less than a third the number oftheoretical stages as compared to a non-pulsating column. A specifictype of reciprocating mechanism is used in a Karr Column which is shownin FIG. 11.

Advantageously, the process and system described herein minimize oxidantcost, and in particular minimize the safety requirements associated withhandling liquid peroxide compounds. In contrast to existing oxidationprocesses based on hydrogen peroxide, the process and system describedherein employs in-situ production of organic peroxides from the feeditself as a source of effective oxygen to further oxidize sulfurcontaining compounds into sulfoxides/sulfones.

In addition, in conventional oxidation processes using an externalsource of hydrogen peroxide, it is usually provided as a 30% H₂O₂aqueous solution with stabilizers. The diluted hydrogen peroxide andstabilizers have a detrimental impact on the capability of oxidizingsulfur compounds.

Furthermore, production of organic peroxides in-situ allows for a singleliquid phase oxidative desulfurization process, rather than a biphasic(liquid-liquid) system as with aqueous peroxides.

Still further, only gas required for the present process is the gaseousoxidant, providing a significant advantage over hydrotreating processeswhich require considerable quantities of gaseous hydrogen.

EXAMPLES Example 1

Cumene peroxide was generated in-situ using Co(Salophen) (structureshown in FIG. 12A) as a catalyst by contacting the cumene and air at 90°C. for 1 hour. The cumene peroxide formation was monitored by a gaschromatography as seen in FIG. 12B.

Example 2

A straight run gas oil, properties of which are given in Table 3, wasdesulfurized using a process scheme similar to that described above withrespect to FIG. 3.

The straight run gas oil was extracted in a counter-current extractorusing furfural as solvent. The extractor was operated at 60° C.,atmospheric pressure at a solvent to diesel ratio of 1.1/1.0. Twofractions were obtained: an aromatic-rich fraction and an aromatic-leanfraction. The aromatic-lean fraction yield was 68 W % and contained3,500 ppmw of sulfur and 11.3 W % aromatics. The aromatic-rich fractionyield was 32 W % and contained 80 W % aromatics and 10,000 ppmw ofsulfur.

The aromatic-lean fraction was hydrotreated in a fixed-bed hydrotreatingunit a over conventional hydrotreating catalyst (Co—Mo on alumina) at 20Kg/cm² hydrogen partial pressure, 320° C., liquid hourly space velocityof 2.0 h⁻¹ and at hydrogen to oil ratio of 280 Liters/Liters. Theproperties of hydrotreated straight run gas oil are given in Table 4.The hydrotreated gas oil contained less than 10 ppmw of sulfur.

TABLE 3 SR Gas Property Unit Method Oil Density @ 15.6° C. Kg/Lt ASTMD4052 0.850 SULFUR W % ASTM D4294 1.3 NITROGEN ppmw 178 Aromatics W %31.5 Paraffins + W % 68.5 Naphthenes Distillation ASTM D2892 IBP ° C. 52 5 W % ° C. 186  10 W % ° C. 215  30 W % ° C. 267  50 W % ° C. 304  70 W% ° C. 344  90 W % ° C. 403  95 W % ° C. 426 100 W % ° C. 466

TABLE 4 Aromatic Lean Property Unit Method Fractions Density @ 15.6° C.Kg/Lt ASTM D4052 0.8381 SULFUR W % ASTM D4294 0.35 NITROGEN ppmw ASTMD4629 91 Aromatics W % 28.5 Paraffins + W % 71.5 Naphthenes DistillationASTM D2892 IBP ° C. 53  5 W % ° C. 187  10 W % ° C. 213  30 W % ° C. 262 50 W % ° C. 299  70 W % ° C. 338  90 W % ° C. 397  95 W % ° C. 420 100W % ° C. 463

The aromatic-rich SR gas oil containing 10,000 ppmw of sulfur wassubjected to air treatment at 90° C. in the presence of Co(Salophen)catalyst for a residence time of 1 hour to generate aromatic peroxides.The total mixture was then oxidized at 75° C. under atmospheric pressurefor 2 hours with sodium tungstate as catalyst (0.5 W %) along withacetic acid as a phase transfer agent. The oxidation by productssulfones were removed by extraction and adsorption steps. The aromaticfraction, which contained less than 10 ppmw of sulfur after oxidation,extraction and adsorption steps, is then sent to diesel pool andcombined with the hydrotreated aromatic lean fraction. The final gas oilfraction contained less than 10 ppmw of sulfur.

The method and apparatus of the present invention have been describedabove and in the attached drawings; however, modifications will beapparent to those of ordinary skill in the art and the scope ofprotection for the invention is to be defined by the claims that follow.

The invention claimed is:
 1. A process for conversion ofheteroatom-containing compounds in a hydrocarbon feedstock to theiroxidation products comprising: separating the hydrocarbon feedstock intoan aromatic-lean fraction and an aromatic-rich fraction; contacting thearomatic-rich fraction with an effective amount of gaseous oxidant underconditions effective for organic peroxide generation and to produce amixture containing organic peroxide and heteroatom-containinghydrocarbons; contacting the mixture containing produced organicperoxide and heteroatom-containing hydrocarbons with the aromatic-leanfraction under conditions effective for oxidative conversion ofheteroatom-containing hydrocarbons in the mixture and in thearomatic-lean fraction into oxidation products of heteroatom-containinghydrocarbons.
 2. The process as in claim 1, further comprisingseparating the hydrocarbon feedstock into a first and second portion;and subjecting only the first portion to separation into thearomatic-lean fraction and the aromatic-rich fraction; whereincontacting under conditions effective for conversion ofheteroatom-containing hydrocarbons further comprises contacting thesecond portion for conversion of heteroatom-containing hydrocarbons inthe second portion into oxidation products of thoseheteroatom-containing hydrocarbons.
 3. The process as in claim 2,wherein separating the hydrocarbon feedstock or the aromatic-richfraction into a first and second portion is with a diverter.
 4. Theprocess as in claim 3, wherein the first portion is about 1 V % to about90 V % of the hydrocarbon feedstock.
 5. The process as in claim 3,wherein the first portion is about 1 V % to about 50 V % of thehydrocarbon feedstock.
 6. The process as in claim 3, wherein the firstportion is about 1 V % to about 30 V % of the hydrocarbon feedstock. 7.The process as in claim 2, wherein separating the hydrocarbon feedstockor the aromatic-rich fraction into a first and second portion is with aflash separation apparatus or a distillation unit to produce the firstportion having an initial boiling point in the range of about 300° C. toabout 360° C.
 8. The process as in claim 7, wherein the first portion isabout 1 V % to about 50 V % of the hydrocarbon feedstock.
 9. The processas in claim 7, wherein the first portion is about 1 V % to about 30 V %of the hydrocarbon feedstock.
 10. The process as in claim 7, wherein thefirst portion is about 1 V % to about 5 V % of the hydrocarbonfeedstock.
 11. The process as in claim 1, wherein contacting underconditions effective for organic peroxide generation and contactingunder conditions effective for oxidative conversion ofheteroatom-containing hydrocarbons into oxidation products of theheteroatom-containing hydrocarbons occur in separate vessels.
 12. Theprocess as in claim 11 wherein contacting under conditions effective fororganic peroxide generation occurs in an organic peroxide generationapparatus.
 13. The process as in claim 12 wherein reactions in theorganic peroxide generation apparatus occur in the presence of catalyst.14. The process as in claim 13 wherein the catalyst is a heterogeneouscatalyst.
 15. The process as in claim 14 wherein the heterogeneouscatalyst is a compound having the general formula M_(x)O_(y), where x=1or 2, and y=2 or 5, and where M is an element that is selected from thegroup consisting of the elements of groups IVB, VB and VIB of thePeriodic Table.
 16. The process as in claim 14 wherein the heterogeneouscatalyst is Co(Salophen) or complexes of Co(Salophen).
 17. The processas in claim 13 wherein the catalyst is a homogeneous catalyst.
 18. Theprocess as in claim 17 herein the homogeneous catalyst is a transitionmetal complex.
 19. The process as in claim 11 wherein contacting underconditions effective for oxidative conversion of heteroatom-containinghydrocarbons into oxidation products of the heteroatom-containinghydrocarbons occurs in an oxidative reaction apparatus.
 20. The processas in claim 19 wherein reactions in the oxidative reaction apparatusoccur in the presence of catalyst.
 21. The process as in claim 13wherein the catalyst includes one or more transition metal oxides. 22.The process as in claim 1, wherein contacting under conditions effectivefor organic peroxide generation and contacting under conditionseffective for oxidative conversion of heteroatom-containing hydrocarbonsinto oxidation products of the heteroatom-containing hydrocarbons occurin a common vessel.
 23. The process as in claim 22 wherein reactions inthe common vessel occur in the presence of a bi-functional catalyst. 24.The process as in claim 1, further comprising removing oxidationproducts of sulfur-containing and nitrogen-containing hydrocarboncompounds from a hydrocarbon product stream.
 25. The process as in claim24, wherein removing oxidation products is by one or more of polishing,extraction, adsorption or decantation.
 26. The process as in claim 1,further comprising hydrotreating all or a portion of the aromatic-leanfraction.
 27. The process as in claim 1, wherein only the aromatic-richfraction is contacted with an effective amount of gaseous oxidant. 28.The process as in claim 1, wherein the step of contacting thearomatic-rich fraction with an effective amount of gaseous oxidantoccurs in an organic peroxide generation apparatus, and the step ofcontacting the mixture containing produced organic peroxide andheteroatom-containing hydrocarbons with the aromatic-lean fractionoccurs in a separate oxidative reaction apparatus.
 29. The process as inclaim 2, wherein the step of contacting the aromatic-rich fraction withan effective amount of gaseous oxidant occurs in an organic peroxidegeneration apparatus, and the step of contacting under conditionseffective for conversion of heteroatom-containing hydrocarbons occurs ina separate oxidative reaction apparatus.
 30. The process as in claim 1,further comprising separating the aromatic-rich fraction hydrocarbonfeedstock into a first aromatic-rich portion and a second aromatic-richportion; passing only the first aromatic-rich portion to the step ofcontacting under conditions effective for organic peroxide generation;and passing at least part of the second aromatic-rich portion to thestep of contacting under conditions effective for oxidative conversionof heteroatom-containing hydrocarbons.